Thanks Tom.

I changed your code a little. See the completed code below. Thanks for all your help.
Sub ResetScreenResolution(Optional Dummy As Integer)
     
    Dim x  As Long
    Dim y  As Long
    Dim MyMessage As String
    Dim MyResponse As VbMsgBoxResult
     
    x = Sheets("Sheet3").Range("A1").Value
    y = Sheets("Sheet3").Range("A2").Value
        MyMessage = "Your current screen resolution was originally " & x & " X " & y & vbCrLf _
        & vbCrLf & "Would you like to restore your original screen resolution now (you can change it later if you like)?"
        MyResponse = MsgBox(MyMessage, vbExclamation + vbYesNo, "Screen Resolution")

    If MyResponse = vbYes Then
        Sheets("Sheet3").Range("A1:A2").ClearContents       
        Call Shell("rundll32.exe shell32.dll,Control_RunDLL desk.cpl,,3")
    End If
     
End Sub